24.09 Minds and Machines
Fall 11 HASS-D CI
from the identity
theory to
functionalism
Image by MIT OpenCourseWare.
24.09 F11
1
roadmap
functionalism (a more general
version of the computer
model of the mind)
argument D (D+)
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Kripke’s
objection
behaviorism
the identity theory
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Block, ‘Functionalism’
Cartesian Dualism said the ultimate nature of
the mental was to be found in a special mental
substance. Behaviorism identified mental states
with behavioral dispositions; physicalism in its
most influential version identifies mental states
with brain states. Functionalism says that mental
states are constituted by their causal relations to
one another and to sensory inputs and
behavioral outputs. Functionalism is one of the
major theoretical developments of Twentieth
Century analytic philosophy, and provides the
conceptual underpinnings of much work in
cognitive science.
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Putnam on the identity theory
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The [type-type] identity theorist] has to specify a
physical-chemical state such that any organism (not
just a mammal) is in pain if and only if (a) it
possesses a brain of a suitable physical-chemical
structure; and (b) its brain is in that physicalchemical state…it must be a state of the brain of
any extra-terrestrial life that may be found that will
be capable of feeling pain…
Putnam, ‘The nature of mental states’
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‘replacement’ thought-experiments
a gradual replacement,
one neuron at a time,
with a chip that has the
same input-output
profile
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A RoboCop movie poster.
is this any worse than a
cochlear implant?
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A Six Million Dollar Man poster.
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an (apparent) lesson
minded creatures can in principle be made out
of anything, provided certain structural
constraints are met
you couldn’t make a mind out of Jello, but you
could make one out of silicon chips
Image removed due to copyright restrictions. Bowls of Jell-O.
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lessons from our discussion of behaviorism
mental states are the inner causes of
behavior
the correspondence between mental states
and behavior is many-many
(a) mental state M may produce different
sorts of behavior, depending on the
creature’s other mental states
(b) the same behavior may be produced by
different mental states
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example 1: the mousetrap
The mousetrap
dead/trapped
mouse output
mousey input
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multiple realizability
Images removed due to copyright restrictions. Three different mouse traps.
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the mousetrap is...
Image removed due to copyright restrictions.
Mickey Mouse.
...the simplest sort of functional
kind
since no constraints are placed on
its inner organization, it is also a
behavioral kind
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example 2: the three-coke vending machine
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OpenCourseWare.
initial
states
output
for
25¢ input
next
states
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M3 I0
M2 I0
M1 I0
“25¢”
“25¢”
“25¢”
M3 I1
M2 I1
M1 I1
Images by MIT OpenCourseWare.
M3 I1
M2 I1
M1 I1
11
M2 I0
M1 I0
shut
down
the vending machine...
Image by MIT
OpenCourseWare.
...can be multiply realized
it is a functional but not behavioral kind
what are the functional states M3, I2, etc?
the table tells the whole story
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functionalism
the view that mental states are functional
states—states specified in terms of their
causal relations to inputs, outputs, and
other states
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functionalism and the lessons
1.
mental states can be multiply realized
2.
input-output isn’t enough: it’s what’s in
between that matters (recall the Aunt
Bubbles machine)
3.
mental states are the inner causes of
behavior
4.
the correspondence between mental states
and behavior is many-many
functionalism accommodates all the above
Image removed due to copyright restrictions.
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the three-coke vending machine again
the functionalist says that mental states can be
specified like Mi, Ij - in terms of their causal relations
to each other and to inputs and outputs
Image by MIT
OpenCourseWare.
Image by MIT OpenCourseWare.
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the simple Turing machine table again
similarly, the functionalist says that mental states can
be specified like S1 and S2—in terms of their causal
relations to each other and to inputs and outputs
state
scanned cell
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S1
S2
1
R, S1
H
0
1, S2
H
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philosophical toolkit: a priori and a posteriori
Tool Kit
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(knowable) proposition p is knowable a priori iff p
can be known independently of experience
otherwise, proposition p is knowable (only) a
posteriori
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a posteriori and
necessary:
water=H2O
a posteriori and
contingent:
it’s cloudy
a priori and
necessary:
2+3=5
a priori and
contingent:
??
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reading for next session
Putnam
this paper is difficult and
we won’t be discussing
everything in it: just give
it a skim on the first
reading, concentrating on
the ‘twin-earth’ example
Image by MIT OpenCourseWare.
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24.09 Minds and Machines
Fall 2011
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